Process and apparatus for the reduction of metallic oxid ores



J. W. MOFFAT.

PROCESS AND APPARATUS FOR THE REDUCTION OF METALLIC OXID ORES.

APPLICATION FILED AUG-I5. 1919.

A 1,348,889, Patented Aug. 10, 1920.

2 SHEETSSHEET 1.

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1 J. W. MUFFAT.

PROCESS AND APPARATUS FOR THE REDUCTION OF METALLIC 0x10 ORES.

APPLICATION HLED AUG.15, 1919- 1,348,889. Patented Aug. 10, 1920 5 2 SHEETS-SHEET 2. Q!

n PE JNVENTUR.

UNITED STATES PATENT OFFICE.

JAMES WILLIAM MOFFAT, OF TORONTO, ONTARIO, CANADA.

- PROCESS AND APPARATUS FOR THE REDUCTION OF METALLIC QXID ORES.

Reduction of Metallic Oxid 'Ores, of which the following is a specification.

In my United States Patent No. 1294514 dated February 18th, 1919, I described a process ofreducing metallic oxid ores and producing molten metal therefrom which involves as the first step the reduction of the oxid ores substantially without fusion, and the object of the present invention is to devise a reducing process and apparatus therefor which will produce a metallic product in discrete form suitable for charging to an electric furnace for fusion as de scribed in the above mentioned patent.

I attain my object by means of apparatus which is adapted to lift and relift the charge from the bottom of the closed chamber and drop it again from the upper part in such a way that every particle of the ore is individually and repeatedly presented to the action of a reducing gas generated-in or led into the furnace. 7

The apparatus is illustrated in the accompanying drawings in which- Figure l is a lon furnace;

Fig. 2 an end elevation of the same; and

, Fig. 3 a vertical cross section ofthe same.

In the drawings like numerals of reference indicate corresponding parts in the different figures.

l is a stationary horizontal cylindrical reduction chamben'which is set within a casing 2, preferably'formed of or lined with,

fire brick. This casing is spaced from the shell of th chamber and is adapted to form a combustion chamber by means of which the reduction chamber maybe externally heated. I prefer to use a fluid or pulverulent fuel, and the casing is provided in one of its walls with apertures 3 for suitable burners. An outlet flue of combustion isled from the upper part of the interior of the casing 2, which flue is "preferably provided with a draft control ling damper 8.

The reduction chamber is provided with suitable charge feeding means, and as it is desirable that the charge should be well distributed longitudinally of the reduction gitudinal section of the for the products Specification of Letters Patent. Patented Au0' 10, 192() Application filed August 15, 1919. Serial No. 317,759.

chamber, I prefer to employ a plurality of such charging means. In the drawings I show three tubes l extending upwardly from suitable openings in the top of the reduction chamber through the casing 2. r bove the casing these tubes communicate with hoppers 5. Each tube is provided with at least one and preferably with two sliding gates (iorother suitable means wherebv the tubes may be opened and closed. When two gates are employed as shown, it is possible to feed the charge to the reduction chamber without permitting the ingress of any air other than that contained in the interstices of the charge, the process usually being to open the upper gate and allow the space between the two gates to fill up. The upper gate is then closed and the lower gate opened to allow the portion of the charge between the two gates to drop into the reduction chamber. By repeating this process with each of the tubes 4C the charge is readily introduced into the reduction chamber.

The reduced charge is discharged fromings 9 as may be desired. Of course, any

other sui able means may be employed. For

operating this gate I employ a hand wheel 16 provided with a threaded hub screwed on the threaded stem 17 secured to the end of the gate 10. The hub of the hand wheel is fitted between shoulders formed on a stationary block 18 so that the hand wheel is held from longitudinal movement. It is evident that by rotating the hand wheel the gate 10 may be moved as desired.

Below the discharge openings 9 located an airtight bin 11, the upper part of which fits closely to the reduction chamber so that the products of combustion within the casing 2 are excluded therefrom. The bottom of this bin is provided with a substantially airtight discharge gate 12. The reduced charge may thus be emptied into the bin and air excluded therefrom. The impor- 10 provided with openings 7 tatcd.

tance of excluding air will be understood when it is remembered that at the temperaturesat which reduction takes place re-oxidation will also take place if the charge comes in contact with atmospheric air.

It is necessary to provide means for the escape of gases from the reduction chamber. I therefore provide the flue 13. This fine is provided with an airtight gate 14 which may be operated so that a slight pressure may be maintained in the reduction chamber which materially helps in the exclusion of atmospheric air. In this flue will usuallybe located the inlet pipe of a C0 recorder indicated at 15. r

The most important feature of the furnace is the means provided for securing the exposure of the particles of the ore to the action of the reducing gas. For this purpose I provide the following means. shaft :19is journaled in bearings 20 outside the casing. This shaft extends through the casing. and the ends of the reduction chamber and will be provided at one or both ends with suitable means whereby it may be ro- This shaft carries means for lifting and dropping the charge without causing endwise travel of the same. In the preferred construction a series of spiders 21 are connected to the shaft provided with circular rims. To the rims of the spiders are secured a series of trough-shaped rabbles 22, which are substantially continuous and extend from end to end of the casing. These trough-shaped rabbles are so constructed as to lift as large a proportion'as possible of Y the load they may pick up at the bottom of the furnace to as great a height as possible before discharging it to drop again to the bottom of the furnace. I find that this resultrmay best be obtained by making the mouths of the troughs with their inner edges somewhat forward of the radial planes touching the outer edges of their mouths, and by extending the inner portion of each trough inwardly closer to the shaft than the inner edge of the mouth of the trough. This form is 'most readily obtained by making the portion 23 of the trough nearest to the shaft of a semi-circular form, the diameter of the semi-circle being substantially at right angles to the radial line through the center of the shaft and the center of the semicircle, the trough nearest the inner surface of the reduction chamber being concavely curved with the outer edge of the mouth of the trough adjacent the radial line aforesaid, as shown in dotted lines in Fig. While considerable material dropped as each trough rises, it will be seen that a very considerable portion is carried completely to the top of the chamber before being discharged.

Through one end of the casing is formed a suitable'opening 24 for a pyrometer for the combustion chamber. A suitable opening 25 is also formed through the casing and one end of the reduction chamber for the pyrometer for the reduction. chamber. A sampling opening 26 provided with a suitable plug is also formed through the end of the casing in the end of the reduction chamber between the center and the path of the trough-shaped rabbles 22, so that samples may be readily obtained while the rabbling device is in motion. c

The operation of the apparatus is substantially as follows. A suitable charge is introduced, the ore being in a finely divided condition, and mixed with a suitable quantity of carbonaceous material, and also with a suitable flux if a flux be necessary. The reduction chamber has, of course, been heated to a suitable temperature for reduction and the rabbling device is kept in mo- 5 tion until complete reduction has taken place and the material discharged. It is of the utmost importance to keep the temperaturein the reduction chamber sufficiently low to prevent agglomeration of the re 90 duced ore and also to keep it constantly in I motion as I find that if the ore remains quiescent a certain amount of agglomera tion may take place even with temperature well below that at which the ore generally assumes a sticky condition. The prevention of the agglomeration of the particles of the ore is of the utmost importance in the handling of the material, since if any caking takes place it becomes almost impossible to satisfactorily discharge the material from the reduction chamber and thereafter to feed it from the receiving bin to the electric furnace for fusion asdescribed in the hereinbefore mentioned patent. I find, however that by treating the ore in a finely divided condition in a furnace constructed as herein before described at the proper temperature, that a reduced product can be obtained also a in a finely divided condition and suitable for handling in suitable troughs, pipes, conveyers or hoppers as may be required.

It will be noted that the process described is'not a continuous one and there is no travel of the ore from one end of the furnace to the other. This enables me to operate the rabbles at that speed which secures the best results since-the rate of operation does not positively determine the length of time the ore remains in the reduction chamber. I 12 am enabled therefore to hold my charge in the reducing chamber as long as may be necessary, as determined by the samples taken from time to time, and-to discharge 'all of it in a very short space of time as 25 soon as substantially complete reduction has cylindrical reduction chamber; charge feeding means located at the top of the reduction chamber provided with a substantially air tight gate; a discharge outlet located at the bottom of the reduction chamber and provided with a substantially air tight gate; means moving in closed orbits adapted to lift and re-lift the charge from the bottom of-the furnace without endwise movement in the furnace, and drop it again from the upper part of the furnace.

2. A furnace for the reduction of metallic oxid orescomprising a stationary horizontal cylindrical reduction chamber; charge feeding means located at the top of the reduction chamber provided with a substantially air tight gate; a discharge outlet located at the bottom of the reduction chamber and provided with a substantially air tight gate; continuous troughs extending from end to end of the furnace parallel to the axis of the chamber and moving in closed orbits, adapted to lift and relift the charge from the bottom of the furnace, without endwise movement in the furnace, and drop it again from the upper part of the furnace.

3. A furnace for the reduction of metallic oxid ores comprising a stationary horizontal cylindrical reduction chamber; charge feeding means located at the top of the reduction chamber provided with a substantially air tight gate; a discharge outlet located at the bottom of the reduction chamber and provided with a substantially air tight gate; a rabbler shaft journaled axially of the chamber; and trough shaped rabbles parallel to the axis of the chamber, having their mouths forwardly directed relative to their direction of motion, connected with the shaft and extending lengthwise of the chamber with their outer edges close to the inner surface thereof.

4. A furnace for the reduction of metallic oxid ores constructed substantially as set forth in claim 3 in which each trough is extended inwardly closer to the shaft than the inner edge of the mouth of the trough.

5. furnace for the reduction of metallic oxid ores constructed substantially as set forth in claim 3 in which each trough is shaped in cross section substantially as follows :-nearest to the shaft of a semi-circular form, the diameter of the semi-circle being substantially at right angles to the radial line through the center of the shaft and the center of the semi-circle, and nearest the inner surface of the reduction chamber con 6. A furnace for the reduction of metallic oxid ores constructed substantially as set forth in claim 1 in which a plurality of discharge outlets are provided extending along the length of the furnace, each provided with an airtight gate. 4

7. A furnace for the reduction of metallic oxid ores constructed substantially as set forth in claim 1 in which a plurality of discharge outlets are provided extending along the length of the furnace, each provided with an airtight gate, and also a plurality of feeding means at difierent points along the length of the furnace.

10. A furnace for the reduction of metallic oxid ores constructed substantially as set forth in claim 1 provided with a suitable closed sampling opening in one end between the center and the path of the troughs.

11. A process of reducing metallic oxid ores which consists in introducing a batch of finely divided ore at the upper part of an air tight chamber, heating the same in the presence of a reducing gas, the ore being constantly lifted and dropped through the gas in such a manner that the particles of ore are individually and repeatedly presented to the action of the gas without movement longitudinally of the furnace and until the oxygen is practically all removed,whereby the condition of the ore or of the gases at all parts of the furnace is the same at any given time.

12 A process of reducing metallic oxid ores substantially as set forth in claim 11 in which the temperature is kept sufficiently low and rabbling continued until the material is discharged to prevent agglomeration of the reduced ore so that the products obtained are in a substantially granular form.

13. A process of reducing metallic oxid ores substantially as set forth in claim 11 in which introduction of the ore and withdrawal of the ore take place each at a plurality of points along the length of the furnace.

' of July 1919.

JAMES WILLIAM MOFFAT. 

